Ultra-thin Solar Cells Using 2D Perovskite Get Boost


The two-dimensional coating of the perovskite compound is the basis for efficient solar cells that can withstand environmental corrosion, unlike previous perovskites. Engineers at Rice University have increased the photovoltaic efficiency of two-dimensional perovskite by 18%. Credit: Jeff Fitlow/Rice University

The rice lab found that the 2D perovskite complex contained the right ingredients to challenge a larger product.

Rice University engineers have set a new standard in designing atomic-thin solar cells made from perovskite semiconductors, increasing their efficiency while remaining environmentally friendly.

Aditya Mohite’s laboratory of the George Brown School of Engineering in Rice found that sunlight itself contracts the space between atomic layers in a two-dimensional perovskite enough to increase the efficiency of photovoltaic materials by up to 18%, a surprising jump in an area where progress is often measured in fractions of a percent.

“In 10 years, the efficiency of perovskite has increased from about 3% to more than 25%,” Moheti said. It will take other semiconductors about 60 years to get there. That’s why we’re so excited. “

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Perovskites are compounds with a cube-like crystal lattice and are very efficient optical harvesters. Their potential has been known for years, but they present a dilemma: They are good at converting sunlight into energy, but sunlight and humidity degrade it.

“Solar cell technology is expected to be operational for 20 to 25 years,” said Mohit, professor of chemical and biomolecular engineering, materials science and nanoengineering. “We have worked for many years and continue to work with a large number of highly efficient but unstable perovskites. In contrast, 2D perovskites have excellent stability but are not efficient enough to be placed on surfaces.

“The big problem is making it effective without sacrificing stability,” he said.

Rice engineers and collaborators at Purdue and Northwestern Universities, the US Department of Energy’s National Laboratory of Los Alamos, Argonne and Brookhaven, and the Institute of Electronics and Digital Technology (INSA) in Rennes, France, found that in some two-dimensional perovskites, sunlight was effectively reduced. The distance between atoms, increases their ability to carry current.

Siraj Sedik, a graduate student at Rice University, is preparing to spin a substrate with a compound that solidifies in a two-dimensional perovskite. Rice engineers have discovered that perovskite displays hold promise for efficient and robust solar cells. Credit: Jeff Fitlow/Rice University

“We found that when you ignite the material, you compress it like a sponge and hold the layers together to increase charge transfer in that direction,” Mohit said. The researchers found a layer of organic cations between the iodide above and led to increased interactions between the layers below.

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“This work has important implications for the study of excited states and quasiparticles in which positive charges in one layer and negative charges in the other can talk to each other,” Mohit said. “These are called excitons, which may have unique properties.

“This effect has given us the opportunity to understand and adapt these basic light matter interactions without creating complex heterogeneous structures such as two-dimensional transition metal dichalcogenides,” he said.

The experiments were confirmed by computer models by colleagues in France. “This study provides a unique opportunity to combine advanced simulation techniques, physical investigations using large-scale national synchrotron facilities and the in-situ characterization of operating solar cells,” said Jackie Even, professor of physics at INSA. This paper describes for the first time how the phenomenon of sudden filtration triggers the flow of charge currents in perovskite materials.

2D perovskite solar cells for testing

Wenbin Li, a graduate student at Rice University, prepared a 2-D perovskite solar cell for testing in a solar simulator. Rice engineers have increased the efficiency of 2D perovskite cells while maintaining their toughness. Credit: Jeff Fitlow/Rice University

Both results show that after 10 minutes under a solar simulator with a density of one sun, the two-dimensional perovskite shrinks by 0.4% in length and about 1% from top to bottom. They show that the effect can be seen within one minute under the fifth sun’s intensity.

“It doesn’t seem like much, but this 1% contraction in lattice spacing leads to a significant increase in electron flow,” said Wenbin Lee, a graduate student at Rice and one of the lead authors. “Our research shows a threefold increase in the electronic conductivity of the material.”

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At the same time, the properties of the mesh make the material not easy to deform, even when heated to 80 degrees

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The Celsius scale, also known as the centigrade scale, is a temperature scale named after the Swedish astronomer Anders Celsius. In the Celsius scale, 0 °C is the freezing point of water and 100 °C is the boiling point of water at 1 atm pressure.

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The Fahrenheit scale is a temperature scale, named after the German physicist Daniel Gabriel Fahrenheit and based on one he proposed in 1724. In the Fahrenheit temperature scale, the freezing point of water freezes is 32 °F and water boils at 212 °F, a 180 °F separation, as defined at sea level and standard atmospheric pressure. 

“>F). The researchers also found that the lattice quickly returned to its normal shape once the lights were turned off.

“One of the main attractions of 2D perovskites is that they typically contain organic atoms that act as moisture barriers, are thermally stable and solve the problem of ion migration,” said Siraj Siddik, a graduate student and co-author. “3D perovskites are subject to heat and light instability, so the researchers started layering a 2D layer on top of the perovskite to see if they could get the best of both worlds.

“We thought, ‘Let’s just go with 2D and make it functional,’ he said.

Show me and Aditya Mohti and Siraj your friend

Rice University graduate student Wenbin Lee, chemical and biomolecular engineer Aditya Mohit, and graduate student Siraj Sidhik are leading a project to produce two-dimensional reinforced perovskites for efficient solar cells. Credit: Jeff Fitlow/Rice University

To monitor material contraction in action, the team used two U.S. Office of Science (DOE) user facilities: the National Synchrotron II Light Source at the Department of Energy’s Brookhaven National Laboratory and the Advanced Photon Source (APS) at the Argonne National Energy Department. Laboratory.

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Argonne physicist Joe Strzalka, co-author on the paper, uses APS ultra-bright X-rays to capture tiny structural changes in materials in real time. The sensitive instruments in the Beamline 8-ID-E allow APS to perform “operando” studies, i.e. studies performed when the instrument is subjected to changes in temperature or a controlled environment under normal operating conditions. In this case, Strzalka and colleagues exposed photoactive materials from a solar cell to simulate sunlight while maintaining a constant temperature, and they observed tiny contractions at the atomic level.

As a control experiment, Strzalka and his colleagues also kept the room dark and raised the temperature, noting the opposite effect—the expansion of the material. This indicates that the light itself, not the heat it produces, is causing the transformation.

“For such a change, it is important to do opera studies,” Strzalka said. “In the same way that your mechanic wants to start your engine to see what’s going on inside, we basically wanted to take a video of that shift rather than a single shot. Utilities like APS allow us to do that.”

Strzalka notes that APS is in the midst of a major upgrade that will increase X-ray brightness by up to 500 times. When completed, he says, the brighter beam and faster, clearer detector will increase scientists’ ability to detect these changes more sensitively.

This could help the Rice team modify the material for better performance. “We are on track to achieve over 20% efficiencies with cations and engineering interfaces,” says your friend. “This will change everything in the perovskite field, because then people will start using 2D perovskite for 2D perovskite/silicon and the synonym of 2D/3D perovskite, which allows for near 30% efficiencies. This will make it attractive for marketing.”

Reference: “Lightly Activated Interlayer Shrinkage in Two-Dimensional Perovskite for High Efficiency Solar Cells” by Wenbin Li, Siraj Seddhik, Boubacar Traore, Reza Asadpour, Jin Ho, Hao Zhang, Austin Ver, Joseph Eismann, Yaffee Wang and Justin M. Hoffman, Ioannis Spanopoulos, Jared J. Crochet, Esther Tsai, Joseph Strzalka, Claudine Cattan, Muhammad A. Alam, Mercury J. Kanatzidis, Jackie Even, Jean-Christophe Blancon and Aditya D. Mohti, 22 November 2021, Available here. Natural nanotechnology.
DOI: 10.1038 / s41565-021-01010-2

The paper’s co-authors are Rice graduate students Jin Ho, Hao Zhang and Austin Fehr, undergraduate student Joseph Eastman and exchange student Yaffe Wang, and co-author Jean-Christophe Blancun, a senior scientist in Mohit’s lab; Boubacar Traore, Claudine Cattan of INSA; Reza Asadpour and Muhammad Alam from Bordeaux; Justin Hoffman, Ioannis Spanopoulos and Mercury Kanatzidis from the Northwest; Jared was knitted by Los Alamos and Esther Tsai by Brookhaven.

The Army Research Office, the French Academic Institute, the National Science Foundation (20-587, 1724728), the Naval Research Office (N00014-20-1-2725) and the Science Office of the Ministry of Energy (AC02-06CH11357) supported the research.

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